21. In the constant field model, the maximum operating frequency is scaled by
a) α
b) β
c) α2
d) β2
Answer: a
In the constant field model, the maximum operating frequency is scaled by α. Maximum operating frequency is scaled by α2/β and here in this model β = α.
22. In the constant electric field model, power dissipation per unit area is scaled by
a) α
b) β
c) 1
d) β2
Answer: c
Power dissipation per unit area is scaled by 1 in the constant electric field model. This is scaled by α2/β2 and here in the constant electric field model β = α.
23. Built-in junction potential Vb depends on
a) Vdd
b) Vgs
c) substrate doping level
d) oxide thickness
Answer: c
Built-in junction potential Vb depends on the substrate doping level and this will be acceptable so long as Vb is small compared with Vdd.
24. As the channel length is reduced in a MOS transistor, depletion region width must be
a) increased
b) decreased
c) must not vary
d) exponentially decreased
Answer: b
As the channel length is reduced in a MOS transistor, depletion width must also be scaled down to prevent the source and drain depletion regions from the meeting.
25. Supply voltage Vdd is scaled by
a) α
b) β
c) 1/α
d) 1/β
Answer: d
Supply voltage Vdd is scaled by 1/β. All voltages are scaled by 1/β.
26. If the doping level of substrate Nb increases then depletion width
a) increases
b) decreases
c) does not change
d) increases and then decreases
Answer: b
If the substrate doping length Nb increases then depletion width decreases because depletion width is inversely proportional to Nb.
27. Maximum electric field can be given as
a) V/d
b) d/V
c) 2V/d
d) d/2V
Answer: c
The maximum electric field can be given by 2V/d and this is induced in a one-sided step junction.
28. The size of a transistor is usually defined in terms of its
a) channel length
b) feature size
c) width
d) thickness ‘d’
Answer: a
The size of a transistor is usually defined in terms of its channel length L because feature size only gives area capacitance etc.
29. What is the minimum value of L to maintain transistor action?
a) d
b) d/2
c) 2d
d) d2
Answer: c
The channel length L should be at least 2d to maintain the transistor action and to prevent punch-through.
30. Channel length L depends on
a) substrate concentration
b) Vgs
c) Vt
d) Vds
Answer: a
Channel length L depends on the supply voltage Vdd and substrate concentration Nb.
